1. Field of the Invention
The present invention is generally related to a water injector for use in conjunction with exhaust passages and, more particularly, to a system by which water is injected from a common conduit into both the primary and idle relief exhaust passages of an outboard motor.
2. Description of the Prior Art
Those skilled in the art of marine propulsion systems and, more particularly, outboard motors, are familiar with various ways of cooling the exhaust gases emitted by an internal combustion engine of a marine propulsion system. One known method of reducing the temperature of exhaust gas, as it flows from an internal combustion engine to an exhaust pipe and is emitted from the marine propulsion system, is to spray water directly into the exhaust gas stream. Other methods include the provision of water jackets and other water reservoir cavities to absorb heat from structures through which the exhaust gases pass.
U.S. Pat. No. 5,149,284, which issued to Kawai on Sep. 22, 1992, describes an exhaust system for an outboard motor. The invention is adapted to be embodied in an outboard motor that is comprised of a power head having an internal combustion engine surrounded by a protective cowling. The engine includes an exhaust port in communication with an exhaust pipe for discharging exhaust gases from the engine. A steering shaft is affixed to the driveshaft housing by upper and lower connections which include elastic bushings. An upper reservoir receives cooling water from the engine to cool structures adjacent the exhaust pipe and specifically the elastic bushings. The reservoir is dammed up on the forward side by the bushing and receives cooling from the cooling water.
U.S. Pat. No. 5,740,670, which issued to Woods on Apr. 21, 1998, describes a water jacketed exhaust pipe for marine exhaust systems. A water jacketed exhaust pipe comprises an inner liner, an outer shell, and a spray ring. The inner liner includes an internally tapered section which clips the turbulence that occurs along the inner walls of the liner. As a result, fluid expelled from the spray ring will not migrate into the inner liner where it can cause severe corrosion.
U.S. Pat. No. 6,035,633, which issued to Woods on Mar. 14, 2000, describes a water jacketed exhaust pipe for marine exhaust systems. This patent is closely related to U.S. Pat. No. 5,740,670 and addresses similar functions.
U.S. Pat. No. 6,151,892, which issued to Brewer et al. on Nov. 28, 2000, discloses an internal combustion engine with programmed water injection into its exhaust system. An exhaust system for an internal combustion engine used in a marine propulsion system is provided with a water injection system by which water can be injected into the exhaust system. An engine control unit, which comprises a microprocessor, is used to select the rate of water injection into the exhaust system as a function of several predefined parameters. For example, engine speed and throttle position can be used by the microprocessor in the engine control unit to select a predefined rate of water flow into the exhaust system by selecting a predefined valve position, for an electronically controlled valve, that has been preselected and stored in a microprocessor.
U.S. Pat. No. 6,406,344, which issued to Bland et al. on Jun. 18, 2002, describes a marine exhaust with dual cooling. A watercraft having two sources of cooling water for injection cooling of hot exhaust gases being conveyed through an exhaust pipe upstream of a muffler is described. The first water source may be an active apparatus such as an engine cooling apparatus. The second source of water may be a passive apparatus such as a Pitot tube formed in the sterndrive of the watercraft. By providing two independent sources of cooling water, the probability of exhaust component failure is significantly reduced.
U.S. Pat. No. 6,537,116, which issued to Nakata et al. on Mar. 25, 2003, describes a cooling system for an outboard motor. The cooling system includes an improved construction that can inhibit a housing unit of the outboard motor from absorbing heat that causes discoloring of the unit. The outboard motor includes a power head that has an engine. The housing unit depends from the power head. An exhaust conduit is arranged to discharge exhaust gases from the engine. At least a portion of the exhaust conduit extends through the housing unit. A cooling system is arranged to cool at least a portion of the exhaust conduit by coolant. The cooling system includes an inner coolant pool surrounding the portion of the exhaust conduit and an outer coolant pool surrounding the inner coolant pool. The cooling system supplies the coolant to the inner and outer pools. The coolant supplied to the outer pool is cooler than the coolant supply to the inner pool.
U.S. patent application Ser. No. 10/182,019, which was filed on Dec. 20, 2001 by Ford et al., describes a marine wet exhaust system. The system injects water into the exhaust flow for cooling and attenuating noise and includes a particulate capture and containment system for removing particulates and water contaminants from the exhaust gas and the waste cooling water of the discharge.
U.S. Pat. No. 6,644,024, which issued to Powers et al. on Nov. 11, 2003, discloses an exhaust system for a marine engine. The exhaust system provides individual exhaust gas conduits that are maintained separately from water conduits until the individual exhaust gas conduits can be combined within a common exhaust gas conduit. This combination of exhaust gas streams allows the amplitude of negative pressure pulses to be damped, by combination with each other, prior to the mixing of cooling water with the exhaust gas streams. Later, the combined exhaust gas stream can be mixed with a combined water stream.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In certain outboard motor applications, an idle relief exhaust passage is used in addition to a primary exhaust passage. It would therefore be significantly beneficial if a water spray cooling system could provide cooling water to both the idle relief exhaust passage and the primary exhaust passage through the use of a single water conduit.